Encoded sheet material

ABSTRACT

An encoded sheet material includes a sheet of material having a first surface, a second surface disposed opposite the first surface and an edge extending between the first surface and the second surface and peripherally about the sheet of material, the edge having indicia arranged thereon to form a code uniquely identifying the sheet of material. A system for managing an encoded sheet of material, includes a code reader operative in conjunction with the encoded sheet of material for reading the code, a sheet processing apparatus for reading information from and/or writing information to at least one of the first and second surfaces, and a processor in communication with the code reader device and the sheet processing apparatus for associating the information with the read code.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of copending U.S. applicationSer. No. 09/643,628 filed Aug. 21, 2000, the contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates generally to encoded sheet material, andmore particularly to systems and methods for managing encoded sheetmaterial having information recorded thereon.

BACKGROUND OF THE INVENTION

[0003] Despite the publicity about the paperless office, paper remainsan important media in today's working environment. Many efforts havebeen made to integrate paper documents with computer-based informationsystems. These efforts generally involve two scenarios. The firstscenario involves scanning an existing physical document to create adigital copy, assigning a digital file name and then managing thedigital copy as any other digital file. The second scenario involvescreation of a physical document from an existing digital document orfile such as by printing. To aid in the integration process, a barcodeor a Dataglyph may be printed or otherwise attached to a physicaldocument. Dataglyphs are generally less visually disruptive thanbarcodes. Both barcodes and Dataglyphs provide a means for the computerto grasp intentionally printed information on the paper document. Sinceboth are generally applied at the time the information is recorded onthe sheet of paper (but may be applied later through the use of anadhesive label), both generally appear on the same face of the sheet ofpaper as the recorded information.

[0004] At the organization level, many documents, such as contracts,reports, files, technical documentation, etc., have to be physicallystored for legal, administrative or operational reasons. Attention mustbe paid to their indexing and classification in order to keep documentretrieval cost at an acceptable level. One solution is to physicallyattach a barcode or Dataglyph to an existing paper document and scan thedocument into the computer-based information system.

[0005] Having a record of a paper document in a computer-basedinformation system does not solve the problem of knowing where theactual paper document is located. Even if location information is storedat the time the paper document is input into the system (such as whenthe barcode or Dataglyph is read by the computer-based informationsystem), the paper document may have been moved when a user retrieved itand later replaced it.

[0006] Most paper documents in offices do not contain barcodes orDataglyphs and are not part of a computer-based information system. Mostoffices have piles of document on shelves, desks and the like that areclassified in an ad-hoc and personal manner. Finding a document in oneof these ad hoc filing systems often means browsing through severalpiles to find a particular document.

[0007] The verification that a paper or hard copy version of a documentis an original, as opposed to a copy or imitation, is important in manybusinesses and legal transactions. Examples include contracts, stockcertificates, bank notes, premium bonds, etc. Verification ofauthenticity of an original document has become harder to perform sincemodern techniques enable the production of high quality copies which arefrequently difficult to detect from the original. Even if an originalpaper document included a barcode or Dataglyph on the face of thedocument, any copy of the paper document will also include the samebarcode or Dataglyph.

[0008] Much work has been done in order to verify the integrity of thecontent of a hardcopy document as well as its origin (this is referredto as authenticating a document). Verifying the content and origin(authenticating) of a hard-copy document consists of making sure thatits content was not tampered with, and that it really originates fromthe supposed source. This prevents manipulation of the content of adocument, while true (i.e. not manipulated) copies remain possible.Originality check is concerned with discriminating copies from theoriginal hardcopy document. The problem of originality is closelyrelated to the problem of authentication because in most cases whereoriginality is important, the content is also important. However, insome cases the originality of a sheet of paper itself is important,independently of its content. Consider for instance the case of a sheetof paper being circulated to collect signatures for a petition. When itcomes back, the originator expects to have the original sheet (and not apossibly manipulated copy).

[0009] The use of edge marking of sheet materials has been proposed forvarious applications. U.S. Pat. No. 5,085,417 to Copham, Method ofEncoding Stacks of Printed Materials, describes a process for using edgemarkings to identify one customer's order for form checks from anothercustomer's. During manufacture of a sheet of checks, a coded image isprovided at the cutting boundaries of the stock sheets, so that when thechecks are cut from the stock, an identification code appears on thechecks when viewed from the edge. The edge-visible code is obtained bycutting the paper precisely where marks are located. A different code isprovided for each customer to enable workers to look at the stackedcheck books at the edge to determine if another customer's checks wereerroneously placed.

[0010] U.S. patent application Ser. No. 09/222,920 filed Dec. 30, 1998,Encoded Sheet Material and Sheet Processing Apparatus Using EncodedSheet Material, which is assigned to the same assignee as thisapplication, describes pre-marking of edges of paper reams/stacks(during manufacture) with information related to the paper's physicalproperties (e.g. its weight, color). This encoded information is readand used by printers (and other recording devices which recordinformation on the faces of the sheet material) when selecting paperfrom paper trays.

SUMMARY OF THE INVENTION

[0011] An encoded sheet material, according to the invention, includes asheet of material having a first surface, a second surface disposedopposite the first surface and an edge extending between the firstsurface and the second surface and peripherally about the sheet ofmaterial, the edge having indicia arranged thereon to form a codeuniquely identifying the sheet of material. A system for managing anencoded sheet of material includes a code reader operative inconjunction with an encoded sheet of material for reading an edge code;wherein the encoded sheet of material has a first surface, a secondsurface disposed opposite the first surface and an edge extendingbetween the first surface and the second surface and peripherally aboutthe sheet of material, the edge having indicia arranged thereon to forma code uniquely identifying the sheet of material; a sheet processingapparatus for reading information from and/or writing information to atleast one of the first and second surfaces of the encoded sheetmaterial; and a processor in communication with the code reader and thesheet processing apparatus for associating the information with the edgecode.

[0012] By providing each sheet of material with a unique edgeidentifier, any information that may be recorded on the sheet ofmaterial may be associated with that sheet of material. By placing theunique identifier on the edge, both surfaces are available for recordinginformation. The edge marking can be made with a visible or an invisibleink. If the recording device includes an edge reader coupled to aprocessor with a memory, whenever a user makes a copy of an electronicfile, the recording device reads the edge marking on each sheet ofmaterial used, and the processor associates that sheet of material withthe electronic file. This association can be stored in memory. Thisfeature is useful for tracking or monitoring physical copies of anelectronic file. Additional information or meta data may also beassociated with the electronic file.

[0013] The association information may be stored and used for otherpurposes, such as monitoring the number of copies made of a particularfile, for monitoring the location of the copies and for monitoring thenumber of sheets of material used. The association information can bemade or updated at any time. For example, if an electronic file isprinted on a sheet of material with a unique edge marking, thatassociation may be made and stored in a memory at the time of printingor later. If that recorded sheet of material is used to make aphotocopy, an edge reader in the copier can make an association of theread edge marking of the “original hard copy” with the edge marking ofthe sheet of material used to make the photocopy. This information maybe stored in memory and can be used to update the associationinformation with the original electronic file and create a newassociation for the “original hard copy.”

[0014] Retrieving information associated with a sheet is accomplished byreading its edge identifier and querying the infrastructure to retrievethis information, given the identifier. Preferably, sheets of materialare pre-marked at production time. If pre-marked at production time,each sheet can be given a code identifying the ream to which it belongsas well as uniquely identifying that sheet. The code can include aportion identifying the ream, manufacturer, and other information that auser might require. Some reams of sheet material may be specially codedwith special visible and/or invisible inks and used as special bondpaper for financial instruments, for example. Indeed, some organizationsmay wish to reserve special reams of material.

[0015] Edge-readers can either be embedded in the recording devices(such as printers, facsimile machines, photocopiers, shredders, etc.) oraffixed in work places (e.g. desktops). The edge readers are coupled toa computer or network where the read association information may be readand/or written. The edge readers enable the automatic association ofprinted-sheet <-> document. Users may also use any sheet of a documenteither to obtain related service by passing the sheet through anedge-reader, or to establish an association in a similar way.

[0016] Documents in paper form are largely used in almost allbusinesses. Documents are frequently stored in an ad-hoc manner (e.g.,on personal shelves in an office) or formally (e.g., legal orcontractual documents are stored in filing cabinets, etc. in banks,administration offices, etc.). Document classification and retrieval isoften problematic and costly. The method of the invention providescomputer support to these two tasks, without disrupting the user'snormal work practice, and requires less effort. The invention enablesdocuments to be automatically indexed in place (i.e., in their normalstorage area) and retrieved by obtaining storage information from acomputer-based system.

[0017] The encoded sheet material of the invention may be used to indexand manage physical documents. Indexing and managing physical documentsgenerally involves four steps. First, the physical documents must beindexed, which often includes generating some form of unique identifier.Then the physical documents must be inserted in the storage area, i.e.,in accordance with some classification scheme. Retrieving the storedphysical document involves searching through the storage area using theclassification scheme. Finally, after use, the document must bere-inserted into the storage area, which location may be different fromthe original location.

[0018] Physical documents may be edge marked and the edge markings usedto index and retrieve them from their storage locations. A method ofmanaging a physical document, wherein the physical document includes atleast one sheet of material, includes marking an edge of the at leastone sheet of material with indicia arranged to form a code identifyingthe sheet of material, storing the physical document in a storagelocation, indexing the physical document by associating the code withthe storage location, and storing the indexing information in acomputer-based information retrieval system. A method of retrieving aphysical document stored in a storage location, includes obtaining acode associated with the physical document, wherein the physicaldocument includes at least one sheet of material having a first surface,a second surface disposed opposite the first surface and an edgeextending between the first surface and the second surface andperipherally about the sheet of material, the edge having indiciaarranged thereon to form the code identifying the sheet of material, andinformation recorded on at least one of the first and second surfaces ofat least one of the sheets of material, using a scanning device to scanthe storage location for the code, and when the output of the scanningdevice indicates the location of the sheet of material having code,retrieving the physical document.

[0019] The invention provides a computer-implemented system for theindexing, storage and retrieval of paper document from piles, filingcabinet, shelves and more generally from document storage areas wheredocument edges are visible. By using a robust code, such as a largebarcode on the edge of the documents, which is visible (to theparticular scanning device) on the edge of the documents, physicaldocuments may be input into a computer-based system and located forretrieval. In addition to storing the edge codes and locationinformation, images of the storage area (shelves, piles, etc.) may alsobe stored in the computer-based system. Documents can be located byscanning the storage location for the document's edge code or byaccessing the computer-based system and retrieving the storage location.

[0020] Since each sheet of paper holds a unique identifier (preferably)pre-marked on its edge at production time, indexing is automatic; thepre-marked edge codes constitute the minimal required index. However,this does not preclude the use of other forms of indexing, in addition.Since the physical documents can be easily retrieved (by scanning stacksof files for their edge codes), storage of physical documents becomes assimple as stacking documents as they arrive. However, any otherclassification scheme can also be used. Documents must be stacked sothat the edge codes can be read. Physical document retrieval is computeror network supported; the computer or network indicates via an outputdevice where the document is located. For example, the computer maydisplay an image of the storage area where the document is located.Re-insertion of a physical document is equally simple.

[0021] An original document is one from which a copy, reproduction ortranslation is made. In the case of a contract, the original contract isthe one (or ones in the case of duplicate originals) with the originalsignatures affixed to it. Originality goes to a document's content aswell as physical integrity (i.e., the particular sheets of paper used).Authenticity of a document goes to the integrity of the information,i.e., whether the information conforms to the information in theoriginal. An authorized copy of an original document, is authentic if itconforms to the original so as to reproduce essential features. Theinvention enables the authentication of originals as well as copies. Theinvention provides a method of authenticating the sheets of paper(material) on which documents are recorded as well as authenticating theinformation on the sheets of material.

[0022] A method of creating an authenticatable sheet of material,according to the invention, includes measuring at least one physicalproperty of the sheet of material; marking an edge of the sheet ofmaterial with indicia arranged to form a unique code identifying thesheet of material, wherein the sheet of material includes a firstsurface, a second surface disposed opposite the first surface and anedge extending between the first surface and the second surface andperipherally about the sheet of material; and recording the measuredphysical property in a measure database indexed by the edge code. Toverify the validity or authenticity of a sheet of material, the edgecode is read, the same physical property is measured and the measuredvalue is compared with the previously stored value extracted from themeasure database. If the two are substantially equal, the sheet ofmaterial is authentic.

[0023] The use of edge codes and physical property measures can be usedto authenticate a document, i.e., a sheet of material on whichinformation has been recorded, and verify its originality. A method ofcreating an authenticatable physical document which includes informationrecorded on a surface of the sheet of paper includes using the edge codewith the information to generate an encryption hash, digitally signingthe encryption hash and recording the digitally signed encryption hashon a surface of the sheet of material. If a physical property has beenmeasured and indexed in a measure database, the originality of the sheetof material can be verified as well. A digital signature does not hidethe content of the information, but is used primarily to guarantee theidentification of the sender of the information and its integrity. Foradded security, the encryption hash may be encrypted rather than justdigitally signed.

[0024] Verifying the authenticity of a sheet of material involvesreading the digitally signed hash on the document, decrypting it,generating a new hash from the edge code and a portion of theinformation. The two encryption hashes are then compared. If they areequal, the document is authentic. Additionally, the edge code can beused to determine if the sheet of material is original, by measuring thephysical property and comparing its value to the value stored in themeasure database.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a schematic of an example edge marking according to theinvention;

[0026]FIG. 2 is a diagram of a scheme for an edge marking including aream marking and individual sheet marking;

[0027]FIG. 3 is a perspective diagram of an edge reader reading anedge-marked sheet of material;

[0028]FIG. 4 is a schematic of an apparatus for managing a sheet ofmaterial according to the invention;

[0029]FIG. 5 is a flow chart of a method of indexing and retrievingphysical documents according to the invention;

[0030]FIG. 6 is an example of 12 characters in Code 39 barcode;

[0031]FIG. 7 is an example of the code “E-PLACARD” in Code 39 barcode;

[0032]FIG. 8 is a photograph of a 30-page document with the code of FIG.7;

[0033]FIG. 9 is a photograph of the barcode extracted from FIG. 8 andenlarged vertically;

[0034]FIG. 10 is a photograph of a screen showing the results of astandard barcode reader reading the barcode in FIG. 8;

[0035]FIG. 11 is a photograph of an image of the location of theE-PLACARD document;

[0036]FIG. 12 is a schematic of a method of creating an authenticphysical document;

[0037]FIG. 13 is a schematic of a method of authenticating a physicaldocument; and

[0038]FIG. 14 is a schematic of a method of authenticating a sheet ofmaterial.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Most sheets of material, such as paper sheets have six faces, twoof them being commonly used: the so-called recto (first surface) andverso (second surface). The four other faces, the edges, may be used touniquely identify each sheet and, optionally, the ream it comes,manufacturer and so on. If a ream identifier is used as part of theunique sheet code, each sheet in the ream will receive the same uniqueream identifier, in addition to a unique sheet identifier. Theseidentifiers can be marked with visible or invisible ink.

[0040] Typical A4 paper sold today presents on the long and short edgesa combined edge surface of 297×0.1 mm² and 210×0.1 mm², respectively. Arobust code can be easily devised to fit within this size constraint. (Arobust code is one which can be easily read on the edge of a singlesheet of material and also affords a sufficiently large number of codesfor the anticipated amount of sheets of material to be used.) Forexample, a 64 bit long code made of 1 mm wide bars on a 2 mm grid wouldrequire 128 mm, which leaves enough room (say 64 mm for 32 bits of errorcode) for error correction code. In total this code (with errorcorrection) would require 192 mm, and would also fit on letter sizesheets (8½ inches by 11 inches). A typical edge thickness of 0.1 mm issufficient height to write the bar constituting the code. For instance,to give an order of magnitude, the dots of a 600 dpi printer are 0.04 mmhigh. Two of these dots fit on the edge height of 0.1 mm. Thus the edgesurface of typical paper sheets is thick and long enough to hold theexample robust codes. A 64 bit long code provides enough unique codes toenable each inhabitant of the earth to consume 80,000 sheets of paper(material) per day for over 100 years.

[0041] There are many schemes which may be used to create a unique codeto mark the edges of sheets of material. In addition to a unique sheetidentifier, the edge code may also include information identifying themanufacturer, date of manufacture, a ream identifier, etc. Two specificexamples will be described herein, however, the invention is not limitedto only these two. The exemplary coding schemes described below includea unique sheet identifier and a ream identifier.

[0042] The first scheme uses the long edge for the sheet identifier andthe short edge for the ream identifier. Referring to FIG. 1, a sheet ofmaterial, such as paper, 10 includes long edge 13 and short edge 11.Long edge 13 includes ream identifier 14; short edge 11 includes uniquesheet identifier 12. While both identifiers are shown in FIG. 1 as bars,other forms of markings may be used, such as diagonal lines, dots andthe like. These marks may be visible or invisible. Optional recordedinformation 16 may be recorded on surface 15 of sheet 10.

[0043] The second exemplary coding scheme codes the ream and sheetidentifiers on the same edge, thus allowing pre-marking of the twoidentifiers on all four edges, which may be advantageous for someapplications. Referring to FIG. 2, ream 20 includes a plurality ofindividual sheets of material 10 (typically there are 500 sheets in aream). In this coding scheme, the ream identifier and sheet identifierare on one edge. A ream identifier 22 is pre-marked at one section ofthe combined edges. In this embodiment, the ream identifier consists ofbars. The sheet identifier is created by offset line 24, drawn acrossthe entire ream. This marking scheme enables pre-marking of the entireream at the same time. The offset 25 between the offset indicator mark27 and the end of the paper edge 29 is sufficient to discriminate eachsheet of a ream.

[0044] In this example, the value of unique identifier for sheet M of aream of N sheets of material may be computed as the distance 23 or asthe ratio of the distance 23 over the entire distance 23+25. This valuein conjunction with the ream portion 22 provides a unique identifier forsheet M. Ream identifier 22 may also include manufacturer name, date ofmanufacture, type of sheet material, etc.

[0045] For a typical 20 pound ream of photocopy paper (height of 5 cm,sheet thickness of 0.1 mm, and 20 cm of the ream edge dedicated to theoffset line), the offset of two consecutive sheets is 0.4 mm. Inaddition, drawing thicker lines parallel to the offset indicator line 24will assist the edge reader device evaluate each sheet offset (becauseof the regularly distributed small plots on the edge of each sheet).Other alternatives exist, such as any asymmetric curvilinear functiondrawn in place of straight line 24 (provided the curve provides a uniquecode for each sheet).

[0046] By marking sheets of material at production time with industrialmeans, invisible inks, fluorescent dyes or other technical inks may beused (in addition to standard visible inks or a combination of visibleand invisible inks). While it is anticipated that most sheets ofmaterial will be pre-marked, i.e., during manufacture and before aninformation is recorded on the surface, pre-marking is not required.Edges may be marked with a code after a sheet of material has beenprinted or recorded with information. Edge marking after information isrecorded is useful for existing physical documents, such as reports,articles, magazines, books, etc.

[0047] An edge reader is used to read the edge code on a sheet ofmaterial or physical document. Edge readers may be employed on desktopsas individual units or embedded in devices such as facsimile machines,printers, copiers, shredders, etc. An example of an edge reader is shownin FIG. 3. Other edge readers may be used, such as a video camera orlight pen. Referring to FIG. 3, a sheet of material 10 with a markededge 12 passes through edge reader 30. The edge reader 30 reads the edgecode, generates an edge code read signal and sends it to computer 110 ornetwork 100. Computer 110 or network 100 associates the edge code isassociated with other information about the physical document 10, suchas whatever information is recorded on a surface of sheet 10. Asdescribed below, the edge code can also be associated with storagelocation information of the physical document.

[0048] Manual readers may be installed in any place where they allowusers to conveniently read the edge identifier of a sheet of material.Typically, such a reader is affixed on the user's desk and connected toa desktop computer. An edge reader may include digital circuitry coupledwith a bar sensor in front of which the sheets are translated (eithermanually by the user, or automatically when embedded in another device).The bar sensor may be an LED and sensor couple, without any mechanicalparts. The digital circuitry decodes the edge-printed identifier,possibly in reverse direction because of possible rotations of the sheetof paper.

[0049] Referring to FIG. 4, a system for managing a sheet of material isshown. Sheet of material 10 is pre-marked during manufacture with aunique code on an edge. Sheet 10 is provided to edge reader 30 whichreads its code and provides it to processor 50. Sheet 10 may also beprovided to sheet processing apparatus 40 which may be a printer, whichwill print information from a digital file onto a surface of sheet 10 ora scanning device which will read recorded information from a surface ofsheet 10 and create a digital file from it. Edge reader 30 and recordingdevice 40 may be separate devices or edge reader may be embedded inrecording device 42. Recording device 40 reads or writes recordedinformation to processor 50. Processor 50 associates the read edge codewith the recorded information and stores the association in memory 52.Alternatively, processor 50 may store the association information on anetwork 60. Each time the sheet 10 is processed by edge reader 30 and/orrecording device 40, the association information may be updated.

[0050] In addition to creating associations between sheets of materialand digital files, associations may be retrieved using the method andsystem of the invention. If a physical document includes at least onesheet of material with an edge code (and presumably recorded informationon at least one of the sheets), the sheet of material may be read by anedge reader coupled to an information retrieval system. If the read edgecode has been previously associated with some information, thatinformation will be retrieved by sending the sheet of paper through anedge reader and searching for any stored associations with that edgeidentifier.

[0051] Various infrastructures may be used to associate a sheet ofmaterial with an edge code identifier with some information, and toretrieve the latter given an identifier. In particular theinfrastructure disclosed in co-pending, co-assigned U.S. patentapplication Ser. No. 09/276,085 filed Mar. 25, 1999, “Marking MediumArea with Encoded Identifier for Producing Action through Network” andU.S. application Ser. No. 09/276,532 filed Mar. 25, 1999, “ObtainingNetwork Addresses from Identifiers” may be used. These applicationsdescribe how a coded number is resolved to the Internet address of adocument (or action) through indirection via a centralized router anddevises efficient routing schemes (which allow codes of the order of 64bits). Because of the indirection level provided by the router, papercan be sold with the code pre-marked on their edges; association with anexisting reference may be done a posteriori through a software processof linking the code to the document address in the routing tables.

[0052] Because of the important role of paper in workplaces, the abilityto easily associate any piece of paper with electronic information is anessential feature for creating and developing knowledge sharingsolutions. For example pre-marking of unique identifiers on paper sheetsmakes it possible to turn any page of a user's documents into a documenttoken. There is no need to print additional machine-readable code, sincethe sheets are pre-marked, but only to associate the pre-markedidentifiers with the electronic document, or with whatever is needed forfurther usage as document token.

[0053] For example, if sheet processing devices which output printedpaper (printer, fax, copier) are equipped with an edge reader andconnected to the infrastructure of the above described co-assignedapplications, it is possible to associate every printed sheet withapplication-relevant information. For example, a printer associates theproduced document with some electronic information, by associating (therange of) the identifiers of the constituting sheets with it.Optionally, only the first and last sheets are pre-marked sheets inorder to reduce the visual “gray” effect on the edge of printed document(two different paper stacks may be used, one with pre-marked paper andthe other with normal paper). The copier associates the identifier ofthe original paper to its copy's identifier, or possibly resolves theformer before establishing the association. A facsimile machine workssimilar to the printer. In turn, the printed document is known to thesystem and any of its sheets can act as a document token once passed inan edge reader.

[0054] Thus a reprint may be obtained by reading the edge of a documentsheet at a “reprint” edge reader affixed close to a printer or copier.The electronic version of a document may be opened on a computer bypassing the printed version in the desktop edge reader.

[0055] Uniquely identified sheets may be used in conjunction with thesystem described in application Ser. No. 09/276,085 dealing with therecognition of the document the person is using. By combining the two,“Intelligent Papers” may be easily produced. Either the publisher printsthe document on an edge-reader-equipped printer to establish theassociation between the paper document and its electronic counterpart,or it associates the document with the pre-printed ream identifier(s).The latter applies particularly well for large volume as it avoidsreading each sheet identifier when printing and as it reduces theinfrastructure load for association and resolution. The device used bythe user must be equipped with an edge reader in order to identify theelectronic counterpart of the document (by querying the normalIntelligent Paper infrastructure).

[0056] Visible edge codes can be used to index, store and retrievephysical documents. A visible code may be one that is visible to theeye, and it may also be one that is invisible to the eye and visible toa detector, such as an infrared detector. A flow chart of the varioussteps in the method is shown in FIG. 5. The first step is to mark theedge of at least one sheet of a physical document (step 70). Preferablythis is accomplished during manufacture of the sheet of material (suchas paper), but it may also occur after manufacture. For multi-pagedocuments, one or some or all of the individual sheets may be edgemarked with an identifying code. The code is associated with thephysical document, such as by document meta data (e.g., URL, title,author, type, topic, date, file name, or some other convenient referencethat may be user selected). Associating the code with the physicaldocument ties the content of the document to the sheets of material.

[0057] In step 72 the physical document is stored in the desiredphysical storage location (e.g., pile of documents on a desk, filedrawer, room, etc.). In step 74 the code is associated with the actuallocation in storage of the physical document. In step 76, the locationassociation information is stored in a memory. The associationinformation includes document code and location information. It may alsoinclude the meta data previously associated with the code. An image ofthe storage location where the physical document is located may also beassociated with the code.

[0058] If a document is already in a storage location and it has an edgecode, but it has not been indexed into the system, it can be indexed byscanning the storage location for the document's code (step 78). Whenthe code is located (step 80), the storage location is associated withthe code (step 74) and that information is stored in memory (step 76).

[0059] Retrieving a document indexed in the system is accomplished bysearching the system's memory for the document's code (step 82), readingthe location information associated with the code (step 84) and thenretrieving the document from the storage location (step 86).

[0060] There are several ways to make visible a code on the documentedge and to establish the association between the edge-visible code anda document. Preferably, the edge of paper sheets is pre-marked atproduction time with a code uniquely identifying each sheet and eachream of paper; a software infrastructure that permits associating theedge code with some data relevant to the document (usually theidentity—such as the URL of the document—but possibly also with metadata) is provided and edge-reader are provided both embedded in deviceslike printers and copiers and provided to users as a desktop tool.

[0061] The edge marking scheme shown in FIG. 2 may be used. Since mostdocuments will contain several pages, we are interested in the visualeffect of stacking the sheets of a document, where the ream identifiersand offset indicators become aggregated. It is reasonable to assume thatin most cases, most of the sheets of a document come from the same ream.Because several sheets of the printed document have the same reamidentifier, this identifier will become clearly visible on the documentedge. In a similar manner, the document edge will exhibit a portion ofthe offset indicator line, as shown in FIG. 2.

[0062] The combination of the aggregated ream identifier and offset lineportion uniquely identify the document. Note that these marks may beinvisible to the human eye because they are marked with invisible ink,or semi-visible. In some situations it may not be necessary to read theentire code on each sheet of paper. A simplification of the method maybe made by using only the ream identifier. The retrieval service may beslightly degraded; the computer system may indicate several locationsfor the requested document, corresponding to the several documentsprinted from the same ream. An advantage of this simplified versionresides in easier image processing, in particular if only the reamidentifier is written on the short edge of sheet and is therefore verylarge. This simplified version may fit well in office settings, whereseveral users share a printer and there is little chance the same userwill obtain several documents from the same ream.

[0063] In addition to the edge marking described above, other methods ofmarking edges of sheets of paper may also be used in the indexing,storage and retrieval method.

[0064] Once a code is provided on the edge of at least one sheet of thedocument, the code may be associated with the document or the documentmeta data in one of several ways. Preferably, the association isestablished at print time in an automatic manner as described above. Theprinter is equipped with an edge reader, which decodes the unique sheetidentifier, and establishes the association between the document and thesheet identifier. For the association, the infrastructure described inco-assigned patent application Ser. Nos. 09/276,085 and 09/276,532 maybe used. Very little modification is required to implement this system;the printer must have an edge reader embedded or coupled to it. Papersurfaces are free from any mark and can be imprinted with any content.Alternatively, the user may explicitly establish the association oncethe document is printed, by presenting it to a sensor (edge reader,camera, scanner).

[0065] Location information can be stored as an image with the documentassociation information. A camera can be used to obtain an image of thedocument in the storage area. The image can be grabbed either on demand(when a search occurs) or periodically to maintain an up-to-date indexof location of documents. The latter also permits reporting on documentavailability and in some way tracking document usage. An inventory ofstored documents is also available to the user.

[0066] Because of resolution issues, one image may not be adequate toidentify and read edge codes. Obtaining a higher-resolution image of thestorage area, in particular for large areas, is possible, for example,by overlapping snapshots. If overlapping snapshots is insufficient tolocate a document, image mosaicking may be used, but is computationallymore costly (in order to stitch together slightly high-resolutionoverlapping snapshots). Once the computer has determined the location ofa searched document, the location may be communicated to the user bydisplaying n image of the storage area, for instance, with the exactlocation of the document highlighted in the image. This provides anatural and intuitive way of communicating location to users.

[0067] In addition to cameras, a laser detector coupled with a laserbeam may be used to point out the document to the user. A morefuturistic approach would be for the user to wear a computer equippedwith a camera, and to have a glass-mounted screen. Augmented realitytechniques would then allow the user to directly see where the documentis within the storage area.

[0068] The identification of regions holding a code and its decodingrequires image-processing techniques. In order for these techniques towork, the code must have sufficient resolution. While many differentcodes may be used and have the required resolution depending on theimage processing equipment used, we have demonstrated the feasibility ofa widely used barcode named Code 39. Encoding codes of the order of 2⁶⁴bits requires 12 characters, given the alphabet of 42 symbols of theCode 39. Each character encoded in a Code 39 symbol is made up of 5 barsand 4 spaces for a total of 9 elements. Each bar or space is either“wide” or “narrow” and 3 out of the 9 elements in any given characterare wide, giving the code its other name—Code 3 of 9. Consider narrowbars of 1.25 mm and wide bars of 2.5 mm. The 12-character code has atotal length of 196 mm, and fits on the short edge of a sheet (see FIG.6). For the long edge, much thinner bars can be used to preserve roomfor the offset indicator line. For example, using more classical 0.25 mmwidth bars makes the code length back to 4 cm.

[0069] Consider now that a camera with a 1600×1200 pixels resolutiongrabs one picture of an area of 1 meter×0.75 meters]. Each pixelrepresents 0.625 millimeters×0.62 millimeters. Two pixels cover thewidth of one narrow bar. Four pixels cover the width of a wide bar. Thisfits our needs, while not taking into account higher resolution obtainedvia image mosaicking. There may be a problem for documents that do notexhibit a clear image on their edge, e.g. there is no block ofcontiguous pages coming from a single ream that is large enough to forman image. This can happen for a very small document, or for a documentspanning over several reams. The case of paper jam may also slightlytrouble the image of the offset line, although probably not seriously.All of these problems can be handled in two complementary ways. First,the printer can detect these problems when they occur, because it readsthe edge identifier of each sheet. Once a serious problem is detected,it can notify the user and print the document again if the problem wastransient (paper jam, several reams). Small documents may possibly notwork at all, unless additional blank pages (or some special separators)are added to them. Second, the user can detect these problems simply bylooking at the edge of the document (if ink is visible or semi-visible).

[0070] To demonstrate the method of the invention, a 30-page documentedge marked on the bottom (short edge) of each page the barcode shown inFIG. 7. The barcode was printed at the bottom of each page usingMicrosoft Word with a zero width margin on a Xerox DocuPrint 4517. Thebarcode is actually at the bottom of the page, bleeding over onto theedge. When the 30-page document is stacked in with a group of unmarkeddocuments, the stacked, the document edge appears as shown in FIG. 8.FIG. 8 is a photograph of the document taken with a Kodak digital cameraDC50 at a resolution of 756×504 pixels. The picture covers approximately30 cm×20 cm. FIG. 9 is a photograph of the barcode extracted from FIG. 8and enlarged vertically. A standard barcode reader was able to read theencoded value: E-PLACARD (see FIG. 10). When queried for the location ofthe document encoded E-PLACARD, the system returns the image shown inFIG. 11 with stored association information.

[0071] A method of creating an authenticatable sheet of materialincludes using the sheets of material with unique edge codes describedabove. For each uniquely identified sheet of material, such as paper,the measure of some physical property is taken, preferably at productiontime (the measure could be taken any time before the sheet of materialis to be recorded with information). The measure is recorded in ameasure database indexed by the edge code (sheet identifier) of thesheet of material. The proof of originality of an individual sheet ofpaper is established by measuring again the same physical property andby comparing the measure to the original one obtained from the measuredatabase. The unique identifier (edge code) of each sheet of materialpermits retrieval of the original measure (taken at production time orsome previous time) from the database).

[0072] One or more physical properties may be measured and the measuredvalue stored in the measure database. For paper materials, paper fiberarrangement or ink penetration may be measured. The infrastructure forassociating information with a sheet of material described above may beused to associate the measured physical properties with the sheet ofmaterial's edge code. The physical property information may also beassociated with any physical document (in which information such asarticle title, file name, URL, etc. is also stored). For securityreasons, the physical property information may be password protected orotherwise securely protected.

[0073] Having a measure database for storage of measured physicalproperty may be preferred by some users. Others may wish to store themeasured physical property values locally in their own database whereother association information is stored with the edge code. Still otherusers may wish to have the measured physical property informationencrypted and recorded or marked on the edge. An edge reader whenreading the encrypted edge code would have to send the read encryptedportion to a decryption device or ignore it if physical property data isnot needed.

[0074] In a typical hard copy authentication process, a hash-value iscreated on the basis of the document content, for example, by scanningit, extracting text and picture characteristics and compressing thisinformation (with loss) into a hash-value. The hash-value is digitallysigned (it may also be encrypted if the content is to be hidden) andprinted on the document itself, for example, using a privatecryptographic key to sign the hash-value and printing it as a Dataglyphor barcode on the bottom of the document. Authentication consists oftaking the Dataglyph marked document, computing the hash-value given thetext of the document, reading the signed hash-value printed on thedocument, and validating it against the computed one using the publiccryptographic key.

[0075] The invention can also be used to extend existing hardcopydocument authentication methods by inserting the unique edge code of theparticular sheet of material in the document's authentication stamp.Referring to FIG. 12, document 200 includes document text 204 which isprinted on the surface of a sheet of paper which has been edged markedwith edge code 202. An encryption hash 206 is created using both edgecode 202 and a portion of text 204. The hash 206 is then digitallysigned (or optionally encrypted) 210 using private key 208. Thedigitally signed (or encrypted) hash is then printed as a Dataglyph 212on document 200. Preferably the digitally signed (or encrypted) hash isprinted as a Dataglyph, but any other recording method or format, suchas a barcode, may be used. The Dataglyph may be recorded on any portionof the sheet of material: first or second surface or on an unusedportion of the edge.

[0076] By using edge coded sheets of material that have beenadditionally pre-notarized, i.e., the validity of the identifier of anindividual sheet can be verified by reference to a measure database,retrieving the pre-measured physical property and comparing it to themeasured value, pre-notarized paper prevents a forger from producing asheet of paper with a duplicate edge code. A forger may still damage theedge code, rendering authenticity and originality in question.Pre-notarized paper tackles the problem of originality, by ensuring theoriginality of the medium, i.e., a sheet of paper, given its unique edgecode identifier.

[0077] Referring to FIG. 13, document 200 includes edge code 202, text204 and Dataglyph 214 which holds a signed hash-value for the purpose ofauthentication and originality verification. Document 200 was createdusing pre-notarized paper, i.e., text 204 was printed or recorded on asheet of pre-notarized paper. In this example, pre-notarized paper wasproduced as follows during manufacture of the sheet of paper. The uniquesheet identifier 202 was applied to the paper's edge. Some measure ofsome chosen physical property(ies) of the sheet of paper was taken. Thistaken measure was stored in a measure database and indexed by the sheetunique identifier 202.

[0078] In FIG. 13, the process for authenticating the document 200,i.e., whether the text is authentic, is shown. The edge code 202 is readin an edge reader and used with a portion of text 204 to create a newhash value 216. Dataglyph 214 is read and decrypted using public key 220in decryption engine 222 to generate the original hash value. Theoriginal hash value is compared in comparator 224 with the new hashvalue 216. If the result 226 of the comparison indicates the two aresubstantially equal (within the level of loss tolerated by theencryption algorithm), the content (text) of the document 200 isauthentic.

[0079] The next step is to verify that the document is original, i.e.,that the sheet of paper is the same one used when the document 200 wascreated. Referring to FIG. 14, the edge code 202 is read by an edgereader. The edge code 202 is provided to a database access 230 whichconsults measure database 232. Measure database retrieves the physicalproperties measured 234 for that sheet of material indexed by the edgecode 202. Given the type of physical properties measured at productiontime, those same measurements are made again to produce physicalmeasures 236. Measures 234 and 236 are compared in comparator 238. Ifthe result 240 is substantially equal, the paper is original.

[0080] This solution to the joint-problem of authentication andoriginality of hardcopy or physical documents incorporates the uniqueedge code identifier of the sheet in the authentication, content-based,hash-value. The verification consists of reading the edge identifier,computing again the hash-value given the identifier and the documentcontent, and finally validating the computed hash-value against theprinted hash-value using the cryptographic public key. This methodprevents manipulation of the content and prevents copy of the documentbecause the sheet identifier cannot be forged.

[0081] The strength of this method relies on the difficulty of producinga sheet of paper having both a given identifier and some given physicalproperties. With respect to the physical measure, the edge itself may beused as the physical property or characteristic that discriminates eachindividual sheet. For example, the edge mark (identifier) applied on theedge involves applying some type of ink or dye on the edge. The way theink or dye penetrates the paper edge is presumably difficult to forgeand can therefore be a valuable measure. Alternatively, the state of the“surface” of the edge and its geometry constitutes a unique profile. Anadvantage to using the physical characteristics of the edge comes fromthe imposed usage of an edge reader (to read the edge unique identifier)at various steps of the method. If some of these edge readers are alsoable to adequately measure the characteristics above, they will servetwo purposes in one operation, both for the paper producer and for theconsumer.

[0082] There are many schemes for managing the measure database. Thedatabase may be managed by the paper producer that provides a serviceallowing the consumers to check the validity of the sheet identifiers.The database may be managed by a notarial service run by a third party.The consumer may purchase the pre-notarized paper together with therecord of the physical measures. However, in this case, the notarizationmay probably be valid only internally to the customer organization.

[0083] The initial physical measures can be entirely recorded, forexample, as a compressed very high-resolution picture of the pre-markededge. The comparison of the physical measures is then possibly made onthe entire measure, i.e., on the entire edge and not just a portion. Thelevel of comparison may be user defined. For example, the consumer maymake measures that are less accurate than the ones taken at productiontime while still being able to compare the two. This has a positiveimplication in term of cost for the consumer (cheaper machinery, fasterto operate). The invention separates the originality of the medium fromthe authentication of the content.

[0084] The digital signature can include the unique identifier andcontent-based information, regardless of the size and type of physicalmeasures. This leads to either a smaller footprint of the digitalsignature or an increased accuracy for the content representation (e.g.a bigger hash-value of the text). Quick and cheap verifications of theoriginality can be made by reading the sheet unique identifier andchecking it together with the document content against the signedhash-value (without taking any physical measure). The strength of theoriginality verification is directly dependent on the difficulty for aforger to mark a given identifier on the edge of a sheet of paper.However, if special ink may be used, it may require an uncommoninfrastructure and know-how. Similarly, a consumer might avoid verifyingthe originality of the sheet (avoid taking any physical measure) whencomputing the hash-value for a document, to make it easier and cheaper.The paper producer may keep secret some of the measures taken as anadditional protection against forgery of the paper. But some of theproperties should be public, to allow the consumers to run their ownverification with their own devices if they want to do so. The choice ofthe physical properties to measure can evolve over time almosttransparently for consumers, while increasing quality of paperpre-notarization.

[0085] The invention has been described with reference to particularembodiments for convenience only. Modifications and alterations willoccur to others upon reading and understanding this specification takentogether with the drawings. The embodiments are but examples, andvarious alternatives, modifications, variations or improvements may bemade by those skilled in the art from this teaching which are intendedto be encompassed by the following claims.

What is claimed is:
 1. An encoded sheet material, comprising: a sheet ofmaterial having a first surface, a second surface disposed opposite thefirst surface and an edge extending between the first surface and thesecond surface and peripherally about the sheet of material, the edgehaving indicia arranged thereon to form a code uniquely identifying thesheet of material.
 2. The encoded sheet material of claim 1, wherein theindicia are pre-marked during fabrication of the sheet material.
 3. Theencoded sheet material of claim 1, wherein the indicia are marked on theedge after information is recorded on one of the first and secondsurfaces.
 4. The encoded sheet material of claim 1, wherein the sheetmaterial comprises paper.
 5. The encoded sheet material of claim 2,wherein the code is 64 bits long.
 6. The encoded sheet material of claim2, wherein the code is visible.
 7. The encoded sheet material of claim2, wherein the code is invisible.
 8. The encoded sheet material of claim1, wherein the indicia are readable by a scanner device operablyconnected to, and in conjunction with, a computer-implemented processor.9. The encoded sheet material of claim 8, wherein information isrecorded on one of the first and second surfaces.